‘Source Code': A ‘Groundhog Day’ With Scientific Mumbo-Jumbo

There’s always that moment in sci-fi thriller where an authority figure — be it a doctor, a scientist, a military officer or an elected official — explains in an urgent burst of highfalutin mumbo-jumbo the phony science that’s propelling whatever is going on on screen.

We in the audience sit there, listening as closely as we can, trying to grasp the concept or explanation being thrown at us.

It’s hoodoo, of course, but official, smart-sounding hoodoo, and we’re going to have to buy it if we’re going to sit through the rest of the movie and root for the hero or heroine to triumph.

In “The Matrix,” it comes when Neo (Keanu Reeve) is told that he has been existing not in the world he thought he inhabited but rather in the much more sinister and complicated matrix.

In last month’s “Limitless,” it comes when Bradley Cooper’s character is told that, if he just swallows a single, translucent pill, it will allow his brain to function at 100 percent capacity rather than the 10 percent that constitutes normal working brainpower.

And in “Jurassic Park,” it comes when we learn that once extinct dinosaurs have been recreated, thanks to being cloned from DNA taken from traces of dino blood found inside prehistoric insects preserved in amber.

Such explanations are generally served up early, in one- or two-sentence soundbites, and then the movie’s real fun begins as whatever loopy premise we’ve been asked to buy into plays itself out.

The inherent promise here is always that if viewers will just swallow this expository bit of pseudo scientific nonsense (a meteor is coming, a deadly virus is on the loose, aliens are headed to Earth, etc.), what follows will be enough fun and/or scary to justify the willing suspension of belief.

In “Source Code,” a lean (93 minutes), engaging thriller, that explanatory moment comes when an Army pilot, Capt. Colter Stevens (Jake Gyllenhaal), is told there’s a reason he keeps finding himself on a Chicago-bound commuter train that then blows up in a massive explosion. A slightly mad scientist type, Dr. Rutledge (Jeffrey Wright), who clearly in some way is attached to the military, tells the puzzled Army officer that he’s part of a government experiment called, yes, “Source Code.”

Per Dr. Rutledge, the brain retains the memory of its last eight minutes after life ends. That train Stevens finds himself on has already blown up. Stevens, now occupying the body of another man, is being dispatched to revisit the train to figure out, in the eight minutes just before the explosion occurred, who planted the bomb.

Got it? Stevens has to keep being teleported back to the train again and again, observing and picking up on new details each time, until he can figure out who the bomber is. It’s “Groundhog Day” but with the future of the Chicago metro area and its inhabitants at stake.

Director Duncan Jones (“Moon”) and screenwriter Ben Ripley manage to make this all seem almost plausible and certainly suspenseful. Just as he did with “Moon,” Jones brings a sense of humanity and quotidian ordinariness in the midst of the film’s often sterile, hi-tech settings.

In a movie like this, which has to move forward at a fast pace to be effective (and it does), actors don’t get time to slowly shape characters. Nonetheless, Gyllenhaal manages to give some sharp emotional shadings to his young officer, while Vera Farmiga, playing a sympathetic military officer guiding his mission, and Michele Monaghan, as an attractive woman he flirts with on the train, serve with distinction.

“Source Code” may be fake science, but it’s the real thing as a sci-fi thriller.